In typical linear voice coil actuators of the type with moving magnets, a moving field assembly is utilized along with a stationary coil assembly attached to a soft magnetic housing. The soft magnetic housing also serves as a back iron for the magnetic circuit. The field assembly is typically comprised of an axially magnetized cylindrical magnet, sandwiched between two soft magnetic pole pieces. The coil assembly can be formed of several coils located in the circular cavities of the coil base attached to the magnetic cylinder or housing. Normally, the axial length of this magnetic cylinder is minimized for a given field assembly length and the stroke. Typically, no other effects are considered.
U.S. Pat. Nos. 6,815,846 and 6,831,538, naming the same inventor as the subject application, and which are assigned to the assignee of the subject application, disclose linear voice coil actuators having spring characteristics that can be viewed as similar to a “one way” mechanical spring, either in extension or in compression.